The present invention relates generally to underwater face masks and, more particularly, to underwater diving masks having eyepieces or lenses mounted on a flexible gasket.
In the past, a variety of underwater face masks have been used for sporting and other activities such as skin and scuba diving. Early underwater face masks typically had several common features, including a contiguous air space shared by the diver's nose and eyes, generally flat, glass or plastic windows, eyepieces or ports fixed approximately perpendicularly to the wearer's straight-ahead viewing axis, and a flexible rubber or plastic support structure for holding the ports in position and trapping an air pocket against the wearer's face. A contiguous air pocket over both the wearer's nose and eyes, as opposed to a mask covering the eyes only, allows for equalizing pressure inside the mask with ambient water pressure as the wearer ascends and descends in the water. Such equalization is necessary to avoid injury to the wearer.
Such conventional flat-window face masks share a variety of shortcomings. The windows or eyepieces of conventional flat-window masks must be supported out from the face. Above and below water, the wearer's horizontal and vertical fields of view are severely limited by the flexible rubber or plastic structures providing such support, thereby creating a sense of "tunnel vision" and a closed-in, claustrophobic feeling. Above water, conventional flat-window masks provide no more than a 140 degree horizontal by 90 degree vertical field of view. Below water, because of the refraction-induced magnification distortion of an air-water viewing system, discussed more fully hereinbelow, this field of view is effectively reduced to approximately 105 degrees horizontal by 67.5 degrees vertical.
Additionally, conventional flat-window masks suffer quite significant magnification-distortion problems from the difference in refractive indices between water and air. Specifically, objects viewed on an axis perpendicular to the window appear approximately 33% larger and 25% closer than they actually are. The magnification-distortion of objects viewed off-axis is even larger.
Further, conventional flat-window masks create a significant amount of hydrodynamic drag and present a significant risk of slipping off the wearer's face if hit by an unanticipated or oblique-angle wave or current.
These and other flat-window mask problems have attempted to be overcome, with less than satisfactory results, by spherically-shaped eyepieces or lenses used for underwater masks. For example, U.S. Patent Nos. 3,899,244, issued to Mulder on Aug. 12, 1975, and 3,672,750, issued to Hagen on Jun. 27, 1972, disclose underwater masks that use built-in corrective lenses in addition to spherically-shaped lenses to improve viewing under water. As such, these masks do not provide optimum viewing characteristics under water without the use of additional corrective lenses. Other single and multiple lens systems used for underwater face masks that do not provide optimum viewing conditions are disclosed in U.S. Pat. Nos. 3,944,345, issued to Decorato on Mar. 16, 1976; 3,040,616, issued to Simpson on Jun. 26, 962; 2,088,262, issued to Grano on Jul. 27, 1937; 2,928,097, issued to Neufeld on Mar. 15, 1960; and 1,742,412, issued to O'Flanagan on Jan. 7, 1930.
U.S. Pat. No. 4,607,398, issued to Faulconer on Aug. 26, 1986, discloses a strap and retainer used for a diver's mask. U.S. Pat. No. 3,051,957, issued to Chan on Sep. 4, 1962, describes a diving mask having a supporting device used to hold the eyeglasses of a diver. In addition, U.S. Pat. No. 4,856,120, issued to Hart on Aug. 15, 1989, describes a purge valve used for a diving mask and a deflector attached to the mask and used to channel air bubbles expelled during purging to the sides of the mask. Another purge valve used for a diver's mask is disclosed in U.S. Pat. No. 4,241,898, issued to Segrest on Dec. 30, 1980.